1. Field
The disclosure relates to a rubber composition in particular for a tire tread, and more particularly for a tire intended to equip vehicles carrying heavy loads and running at sustained speeds, such as lorries, tractors, trailers or buses, aircraft, etc.
2. Description of Related Art
Some current tires, referred to as “road” tires, are intended to run at high speed and over increasingly long journeys, as a result of the improvement in the road network and of the growth of the motorway network throughout the world. However, since saving fuel and the need to protect the environment have become a priority, it is important for tires to have a low energy consumption. One of the sources of energy dissipation is the heating-up of the tire.
Likewise, it is known that the treads of tires used for civil engineering are particularly sensitive to increased temperature. As it happens, an improvement in the properties of tires, and in particular their wear resistance, is continually sought and, conventionally, an improvement in wear resistance is known to be reflected by an increase in energy consumption.
In order to obtain such an improvement in wear resistance and energy consumption, it is sought to use, in the tread, reinforcing fillers which are finer, in particular “fine” carbon blacks, i.e. carbon blacks which have a CTAB specific surface area greater than or equal to 90 m2/g, or even “very fine” blacks, i.e. carbon blacks having a CTAB specific surface area greater than or equal to 130 m2/g. However, in order to obtain the optimum reinforcing and hysteresis properties imparted by a filler in a tire tread and thus high wear resistance and low rolling resistance, it is generally known that this filler should be present in the elastomeric matrix in a final form that is both as finely divided as possible and as uniformly distributed as possible. Such conditions can be achieved only if this filler has a very good capacity, on the one hand, to be incorporated into the matrix during the mixing with the elastomer and to deagglomerate, and, on the other hand, to disperse uniformly in this matrix.
As it happens, very fine blacks are known to be extremely difficult to correctly disperse in the elastomeric matrix and cause degradation of processibility (compared with the use of less fine blacks at equal content). One solution for those skilled in the art would be the use of plasticizing oil or resin to improve processibility. However, it is known that the use of such plasticizing agents results in a very considerable degradation of the energy at break properties (elongation at break and stress at break properties).